1. Field of the Invention
The present invention relates to methods of producing polypeptides in protease-deficient Trichoderma mutant strains, the protease-deficient Trichoderma mutant strains, and methods of obtaining the protease-deficient Trichoderma mutant strains.
2. Description of the Related Art
Trichoderma has been shown to be useful as a host cell for the recombinant production of polypeptides having biological activity (WO 96/00787, WO 97/26330). Trichoderma hosts with the desirable traits of increased protein expression and secretion may not necessarily have the most desirable characteristics for successful fermentation. The fermentation may not be optimal because of the production of biological substances, e.g., enzymes, detrimental to the production, recovery, or application of a particular polypeptide of interest.
Martinez et al., 2008, Nature Biotechnology 26:553-560, describe the genome sequencing and analysis of the biomass-degrading fungus Trichoderma reesei. Dienes et al., 2007, Enzyme and Microbial Technology 40: 1087-1094, disclose the identification of a trypsin-like serine protease from Trichoderma reesei QM9414. Eneyskaya et al., 1999, Appl. Microbiol. Biotechnol. 52: 226-231, describe an acid protease from Trichoderma reesei. Haub et al., 1990, J. Biotechnology 16: 187-198, disclose the formation of extracellular proteases from Trichoderma reesei QM9414. Hagspiel et al., 1989, Appl. Microbiol. Biotechnol. 32: 61-67, disclose protease activity and proteolytic modification of cellulases from a Trichoderma reesei QM9414 selectant. WO 2006/073839 discloses fungal acidic proteases.
WO 2007/045248 describes use of fungal mutants for expression of heterologous polypeptides.
The present invention relates to improved Trichoderma hosts that combine the capacity for expression of commercial quantities of a polypeptide of interest while being deficient in the production of preotease(s) that can complicate recovery and downstream processing of the polypeptide.